1. Field of the Invention
The present invention relates to a focusing control device, an imaging device, a focusing control method, and a computer readable medium storing a focusing control program.
2. Description of the Related Art
In recent years, with an increase in resolution of imaging elements, such as a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor, there is a rapid increase in demand for information devices having an imaging function, such as a digital still camera, a digital video camera, and a smartphone. The information devices having an imaging function described above are referred to as imaging devices.
In these imaging devices, as a focusing control method which focuses on a main subject, a contrast auto focus (AF) method or a phase difference AF method is employed.
The contrast AF method is a method which acquires contrast of captured image signals obtained in movement stages while moving a focus lens in an optical axis direction as evaluation values and determines a lens position having the highest evaluation value as a focusing position.
JP2015-43042A and JP2013-160925A disclose an imaging device that performs focusing control through the contrast AF method. JP2015-43042A describes a method of acquiring a polynomial approximate curve expressed by two polynomial approximate expressions by a plurality of evaluation values acquired through the above-described method and determining an intersection position of the two polynomial approximate curves as a focusing position.